This invention relates to finely divided particulate inorganic antimony compounds, and more particularly, to antimony oxides and sulfides which are surface modified with an organic titanate compound.
Organic resins and elastomers have been used for a wide variety of purposes. However, many synthetic resins and elastomers generally are flammable, and the use of these materials presents certain problems and dangers. Efforts have been made to improve the flame-retardant and smoke-retardant properties of synthetic resins and elastomers, and such efforts have increased in recent years.
Some suggestions for improving the flame-retardant properties of resins and elastomers involved modification of the polymers themselves such as by introducing the monomeric material into the polymer mixture which should reduce the flammability of the product. For example, it has been known that the flammability and burning properties of polyacrylonitrile can be reduced by copolymerising acrylonitrile with halogencontaining comonomers such as, for example, vinyl or vinylidene chloride. It also has been suggested to incorporate certain flame-retardant additives into resins and elastomers, and various halogen-containing organic compounds have been shown to be effective as flame retardants.
A number of antimony compounds have been used as flame retardants in combination with other flame retardants for various organic resins and elastomers. One commonly used compound is antimony trioxide. One of the difficulties associated with the use of antimony compounds such as antimony oxides and antimony sulfides to improve the flame-retardant properties of flammable organic resins and elastomers is the degradation of some of the other desirable properties of the treated elastomers and resins. Although the incorporation of small amounts of antimony oxides and antimony sulfides in conjunction with organic flame-retardant compounds in flammable resins and elastomers generally improves the flame-retardant properties of the resulting product, the incorporation of such antimony compounds often has an adverse effect on other properties of the resins and elastomers such as flexural strength, impact strength, tensile strength, flexural modulus and hardness.
The above-described adverse effects are not limited to the antimony oxides and sulfides. The literature describes procedures for filling thermoplastic and other polymers with many inorganic oxides, primarily as fillers. Examples of inorganic oxides which have been used as fillers for resins and elastomers include aluminum oxide, zinc oxide, iron oxide, magnesium oxide, titanium dioxide, silicates such as kaolin clay, mica, calcium silicate and aluminum silicate, calcium carbonate such as limestone, etc. In the initial development of this art, the inorganic oxide materials, in particulate form, were introduced and blended into resins and elastomers. The resulting mixtures were molded by conventional methods such as casting, injection molding, extrusion or rotational molding to form inorganic oxide reinforced plastic articles. However, it generally was found that the properties of such filled articles were not as good as expected or desired.
Various suggestions have been made in the literature for improving the results obtained when such inorganic oxide materials are incorporated into resins and elastomers. A number of suggestions for overcoming these problems have involved the use of silicon-containing compounds, and particularly silane coupling agents.
U.S. Pat. No. 3,641,087 describes the use of brominated silane derivatives in combination with metal oxides such as antimony oxides and organic antimonates as flame-retardant additives for synthetic polymer compositions. The separate addition of metal oxides such as antimony oxide and other additives such as silanes and diallyl chlorendates to diallylic phthalate resins is described in U.S. Pat. 3,483,158. Such compositions are reported to be flame retardant.
U.S. Pat. No. 3,793,288 suggests that the bonding relationship between polymers and inorganic fillers may be improved by treating the polymer rather than by treatment of the fillers. Accordingly, U.S. Pat. No. 3,793,288 applies a surface on thermoplastic polymers which comprises an organo-functional silane coupling agent and a copolymer of ethylene and acrylic acid and/or methacrylic acid.
A monoalkoxy titanate coupling agent, isopropyl, 4-aminobenzenesulfonyl-di(dodecylbenzenesulfonyl) titanate has been suggested as being useful to reduce the extractability of antimony oxide and Dechlorane (a halogen-containing flame retardant) when incorporated into certain resins. It has been suggested that the improved bonding results at least in part from the interaction of the amine group of the titanate with the halogen-containing compound.
Considerable effort has been devoted to improving the flame-retardant properties of resins and elastomers in recent years, and the above-discussed prior art merely is exemplary of these efforts.